The present invention relates to optical systems. In particular, the present invention relates to optical systems in data storage devices.
Optical data storage systems access data by focusing a laser beam or other light source onto a data surface of a medium and analyzing the light reflected from or transmitted through the medium. In general, data is stored in optical storage systems in the form of marks carried on the surface of the medium which are detected using a reflected laser light.
Compact discs, which are widely used to store computer programs, music and video, are one type of optical data storage system. Typically, compact discs are permanently recorded during manufacture by stamping the surface of the compact disc. Another type of optical system is a write once read many (WORM) system in which a user may permanently write information onto a blank disc. Other types of systems are erasable, such as phase change and magneto-optic (M-O) systems. Phase change systems detect data by sensing a change in reflectivity. M-O systems read data by measuring the rotation of the incident light polarization due to the magnetic state of the storage medium.
In many prior art optical disc storage systems, the optical head is carried on a mechanical actuator which moves the head across the disc surface. In some more recent data storage systems, the optical head is carried on a slider which flies over the surface of the disc and is located at the end of an actuator arm. A significant portion of the optics in such systems is not carried on the armature. Instead, much of the optics is spaced apart from the armature and light from the optics is directed to slider, for example by directing a beam toward the slider or by using an optical fiber.
An optical data storage system includes an optical disc and an armature adjacent the disc. An optical transducer mounted on the arm provides an optical beam output directed parallel to the plane of the disc. An optical actuator mounted on the arm and positioned in the optical beam adjusts the direction of the optical beam and a mirror is positioned to direct the optical beam in a direction perpendicular to the disc and toward the disc. An optical head is positioned at a distal end of the arm and is adapted to couple the optical beam to the optical disc. An arm actuator is coupled to the arm to move the arm relative to the disc and provide coarse positioning of the optical head relative to tracks on the disc. The optical actuator provides fine adjustment of the optical beam between tracks on the disc which are proximate the optical head due to the coarse adjustment by the arm actuator.